The only time I've heard of people sucessfully using lockers in the front 7.2 diff is when they have swapped in the cast iron diff from a 5 speed ZR2. I've seen 3 or 4 people post up stories who tried it with the aluminum diff and it grenaded on their first trip each time. If you're doing some serious off-roading and really want a front locker then you really should try and find a cast-iron diff.